A surface-coated cutting tool having a coating formed on a base material has conventionally been used. For example, Japanese Patent Laying-Open No. 2013-063504 (PTD 1) proposes a surface-coated cutting tool having a coating including a lower layer and an upper layer. The lower layer is a Ti compound layer. The upper layer is disposed on the lower layer and formed of an Al2O3 layer having an α-type crystal structure. In particular, PTD 1 discloses that this surface-coated cutting tool has a feature that (11-20) orientation is 30 to 70 area % in the interface between the upper layer and the lower layer, and a feature that (0001) orientation is 45 area % or more in the entire upper layer. Meanwhile, PTD 1 does not disclose distribution of (001) orientation in the thickness direction of the α-Al2O3 layer.
Japanese Patent Laying-Open No. 10-204639 (PTD 2) proposes a surface-coated cemented-carbide cutting tool having a hard coating layer formed of an α-type aluminum oxide composite layer. The α-type aluminum oxide composite layer is made up of two or more α-type aluminum oxide unit layers exhibiting different x-ray diffraction patterns. In the x-ray diffraction patterns of the α-type aluminum oxide unit layers, a highest peak appears at any of 25.5°, 35.5°, 37.2°, and 68.4° of 2θ. A ratio (H1/H2) of the highest peak height (H1) to a second-highest peak height (H2) in the same x-ray diffraction pattern is 1.5 to 2.7.
Japanese Patent Laying-Open No. 2000-218410 (PTD 3) proposes a surface-coated cemented-carbide cutting tool having a hard coating layer including an aluminum oxide layer having an α-type crystal structure. The aluminum oxide layer is made up of a lower layer with strong crystal orientation and an upper layer with weak crystal orientation. The ratio of the thickness of the upper layer to the total thickness of the upper layer and the lower layer is 10 to 40%.